SCI Scientists may have solved a huge riddle in Earth’s climate past. It doesn’t bode well for the future.

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Scientists may have solved a huge riddle in Earth’s climate past. It doesn’t bode well for the future.by Chris Mooney

An ancient flood seems to have stalled the circulation of the oceans, plunging the Northern Hemisphere into a millennium of near-glacial conditions.

In 2013, a team of researchers set sail to the eastern Beaufort Sea in search of evidence for the flood near where the Mackenzie River enters the Arctic Ocean, forming the border between Canada's Yukon Territory and Northwest Territories. From aboard the U.S. Coast Guard Cutter Healy in ice-covered waters, the team gathered sediment cores from along the continental slope east of the Mackenzie River. Above, the piston corer is shown in horizontal position, with the gravity corer hanging vertically, ready to be launched.

Thirteen thousand years ago, an ice age was ending, the Earth was warming, the oceans were rising. Then something strange happened – the Northern Hemisphere suddenly became much colder, and stayed that way for more than a thousand years.

For some time, scientists have been debating how this major climatic event – called the “Younger Dryas” – happened. The question has grown more urgent: Its answer may involve the kind of fast-moving climate event that could occur again.

This week, a scientific team made a new claim to having found that answer. On the basis of measurements taken off the northern coasts of Alaska and Canada in the Beaufort Sea, the scientists say they detected the signature of a huge glacial flood event that occurred around the same time.

This flood, they posit, would have flowed from the Arctic into the Atlantic Ocean and shut down the crucial circulation known as the “Atlantic meridional overturning circulation” (or AMOC) – plunging Europe and much of North America back into cold conditions.

“Even though we were in an overall warming period, this freshwater, exported from the Arctic, slowed down the vigor, efficiency of the meridional overturning, and potentially caused the cooling observed strongly in Europe,” said Neal Driscoll, one of the study’s authors and a professor at the Scripps Institution of Oceanography.

The work, published in Nature Geoscience, was led by Lloyd Keigwin of the Woods Hole Oceanographic Institution along with researchers at that institution, Scripps and Oregon State University.

The result remains contested, though, with other researchers still arguing for different theories of what caused the Younger Dryas – including a very differently routed flood event that would have entered the ocean thousands of miles away.

Nonetheless, the story is relevant because today, we’re watching another – or rather, a further – deglaciation, as humans cause a warming of the planet. There is also evidence that the Atlantic circulation is weakening again, although scientists certainly do not think a total shut-off is imminent, and are still debating the causes of what is being observed.

Either way, the new research underscores that as the Earth warms and its ice melts, major changes can happen in the oceans. And could happen again.

The researchers behind the current study, working on board the U.S. Coast Guard Cutter Healy, analyzed sediments of deep ocean mud, which contain the shells of long-dead marine organisms called foraminifera. In those shells, the scientists detected a long-sought-after anomaly recorded in the language of oxygen atoms.

The shells contained a disproportionate volume of oxygen−16, a lighter form (or isotope) of the element that is found in high levels in glaciers. That is because oxygen−16, containing two fewer neutrons and therefore lighter than oxygen−18, evaporates more easily from the ocean but does not rain out again as readily. As a result, it often falls as snow at high latitudes and is stored in large bodies of ice.

“This is the smoking gun for fingerprinting glacial lake outbursts,” Driscoll said. And that means the findings may also represent the trigger for the Younger Dryas.

The thinking is that as the ice age ended and the enormous Laurentide ice sheet atop North America began to retreat, the resulting meltwater fed a bevy of large lakes atop the depressed surface of the continent. That included the massive glacial Lake Agassiz, which stretched from the Great Lakes northwestward across much of Canada.

The approximate maximum extents of major glacial lakes that formed from the retreat of the western Laurentide Ice Sheet.

Prior research had shown that for a while, much of the resulting freshwater drained down the Mississippi River and into the Gulf of Mexico. But at some point, as the ice sheet continued to shrink, the flow of water appears to have been suddenly rerouted to the north or to the east, where it could do more potential damage to the ocean circulation in the Atlantic.

There has long been scientific debate about where all the meltwater actually entered the ocean, though – with some contending that it would have occurred through the St. Lawrence River, which flows past today’s Montreal and Quebec City and thus out into the Atlantic.

The new research holds that, instead, the floodwater exited through the Mackenzie River, which stretches across today’s Northwest Territories, emptying straight into the Arctic Ocean.

It would certainly have been an enormous flow of fresh water. “I would say somewhere between the Mississippi and the Amazon,” Keigwin said.

That could have interfered with the Atlantic circulation, which is crucial because it carries warm water northward, and so heats higher latitudes. Eventually, the waters of the circulation become very cold as they travel northward, but because they are also quite salty, they sink because of their high density and travel back south again.

Freshening is therefore the Achilles' heel of the circulation. And the new study argues that although the glacial water would have entered the seas very far away near the present Alaska-Canada border, it would have then circulated around the Arctic, eventually traveling south past Greenland and entering the key regions that are crucial to the overturning circulation, which tend to be off Greenland’s southern coasts.

Not everyone is convinced, though – including some researchers who have previously published results suggesting that the outburst flood or flow was instead to the east, through the St. Lawrence River.

“They have produced a nice signal of the release of freshwater into the Arctic Ocean, but the conclusions are based on an uncertain chronology which, when trying to tie together events so closely, requires some independent confirmation," Peter Clark, an Oregon State University geoscientist who has published evidence supporting the St. Lawrence River theory, said in an email.

Anders Carlson, Clark’s co-author and colleague at Oregon State University, sent a geological study finding that, as he put it in an email, “the Lake Agassiz waters were clearly routed eastward at the start of the Younger Dryas."

“This does not preclude Younger Dryas-age floods … to the Arctic Ocean,” Carlson wrote, "but it does show that such floods are of local origin and not related to the drainage of Lake Agassiz.”

Both groups, though, think the flow of fresh water from the gigantic lake and from other melting events toward the Atlantic interfered with the ocean’s circulation – they’re just disagreeing about how it got there.

The question thus becomes whether it is possible to even more dramatically interfere with the circulation again – and what could cause that.

“I don’t think there’s any lakes on land that are big enough to do this,” Keigwin said. “It has to come from ice, because that’s the biggest reservoir of freshwater. And Greenland is the ice mass that you would be most suspicious of, because it’s right there poised to do enough damage.”

And yet, Greenland is no Lake Agassiz. “Greenland doesn’t have large land lakes to store the water,” Driscoll said. Rather, it releases steady streams of water in the form of glacial runoff, which often goes straight into the ocean – and it releases huge icebergs that slowly melt.

So nobody is necessarily expecting a sudden outburst flood as Greenland melts. Still, Driscoll and Keigwin both think that Greenland’s steady losses over time, especially if they increase in pace, can build up.

Climate scientists will be quick to point out that even if the Atlantic circulation shows or shuts down, ceasing to transport as much heat and leading to some Northern Hemisphere cooling, the overall global warming trend will still be ongoing and may overpower it. We won’t directly repeat the Younger Dryas, but we can learn from it.

it is strange that this article doesn't mention the mountain of evidence uncovered since 2007 that the massive melting and resulting flood was caused by the impact of a comet or meteor into the glacial ice sheet covering north america then.

it is strange that this article doesn't mention the mountain of evidence uncovered since 2007 that the massive melting and resulting flood was caused by the impact of a comet or meteor into the glacial ice sheet covering north america then.

Not the first time such pooling of ice melt let lose as there is evidence of it happening with last ice age and for many it oddly took place some 9,000. to 8,000. years ago and we have a major sea level rise.
What they are pointing out is where it all went to or that it all poured into the Arctic.

Roughly 12,900 years ago, massive global cooling kicked in abruptly, along with the end of the line for some 35 different mammal species, including the mammoth, as well as the so-called Clovis culture of prehistoric North Americans. Various theories have been proposed for the die-off, ranging from abrupt climate change to overhunting once humans were let loose on the wilds of North America. But now nanodiamonds found in the sediments from this time period point to an alternative: a massive explosion or explosions by a fragmentary comet, similar to but even larger than the Tunguska event of 1908 in Siberia.

Sediments from six sites across North America—Murray Springs, Ariz.; Bull Creek, Okla.; Gainey, Mich.; Topper, S.C.; Lake Hind, Manitoba; and Chobot, Alberta—yielded such teensy diamonds, which only occur in sediment exposed to extreme temperatures and pressures, such as those from an explosion or impact, according to new research published today in Science.

The discovery lends support to a theory first advanced last year in that some type of cosmic impact or impacts—a fragmented comet bursting in the atmosphere or raining down on the oceans—set off the more than 1,300-year cooling period in the Northern Hemisphere known as the Younger Dryas for the abundance of an alpine flower's pollen found during the interval.

The cooling period interrupted an extended warming out of an ice age predicted by slight changes in Earth's orbit (known as Milankovitch cycles) that continues today. And it remains an unexplained anomaly in the climate record.

But a series of cometary fragments exploding over North America might explain a layer of soil immediately prior to the cooling containing unusually high levels of iridium—an element more common in cosmic wanderers like meteoroids than in Earth's crust. Paired with the fact that this layer occurs directly before the extinction of at least 35 genera of large mammals, including mammoths, it is strong circumstantial evidence for a cosmic event.

"Very strong impact indicators are found in the sediments directly above, and often shrouding in the case of Murray Springs, the remains of these animals and the people who were hunting them," says archaeologist and study co-author Doug Kennett of the University of Oregon in Eugene, the son in the father–son team helping to advance the new impact theory. "Is it a comet? Is it a carbonaceous chondrite? Was it fragmented? Was it focused? Based on the distribution of the diamonds, it was certainly large scale."

Preliminary searches further afield—Europe, Asia and South America—have turned up similar minerals and elements in sediments of the same age, Kennett says, and his own work on California's Channel Islands tells a tale of a massive burn-off, followed by erosion and a total change in the flora of the region.

The Younger Dryas impact hypothesis or Clovis comet hypothesis originally proposed that a large air burst or earth impact of one or more comets initiated the Younger Dryas cold period about 12,900 BP calibrated (10,900 14C uncalibrated) years ago.[1][2][3] The hypothesis has been contested by research showing that most of the conclusions cannot be repeated by other scientists, and criticized because of misinterpretation of data and the lack of confirmatory evidence.[4][5][6][7]

The current impact hypothesis states that the air burst(s) or impact(s) of a swarm of carbonaceous chondrites or comet fragments set areas of the North American continent on fire, causing the extinction of most of the megafauna in North America and the demise of the North American Clovis culture after the last glacial period.[8] The Younger Dryas ice age lasted for about 1,200 years before the climate warmed again. This swarm is hypothesized to have exploded above or possibly on the Laurentide Ice Sheet in the region of the Great Lakes, though no impact crater has yet been identified and no physical model by which such a swarm could form or explode in the air has been proposed. Nevertheless, the proponents suggest that it would be physically possible for such an air burst to have been similar to, but orders of magnitude larger than, the Tunguska event of 1908. The hypothesis proposed that animal and human life in North America not directly killed by the blast or the resulting coast-to-coast wildfires would have likely starved on the burned surface of the continent.

Evidence

The evidence for an impact event includes charred carbon-rich layers of soil that have been found at some 50 Clovis sites across the continent. The layers contain unusual materials (nanodiamonds, metallic microspherules, carbon spherules, magnetic spherules, iridium, platinum, charcoal, soot and fullerenes enriched in helium-3), which are interpreted to be potential evidence of an impact event, at the very bottom of black mats of organic material that marks the beginning of the Younger Dryas,[9][10] and it is claimed these cannot be explained by volcanic, anthropogenic, or other natural processes.[3]

Recent research has been reported that at Lake Cuitzeo, in the central Mexican state of Guanajuato, evidence supporting a modified version of the Younger Dryas impact hypothesis—involving a much smaller, non-cometary impactor—was found in lake bed cores dating to 12,900 BP. The reported evidence included nanodiamonds (including the hexagonal form called lonsdaleite), carbon spherules, and magnetic spherules. Multiple hypotheses were examined to account for these observations, though none were believed to be terrestrial. Lonsdaleite occurs naturally in asteroids and cosmic dust and as a result of extraterrestrial impacts on Earth. The analysis of the study has not been confirmed or repeated by other researchers.[11] Lonsdaleite has also been made artificially in laboratories.[12][13]

A 100-fold spike in the concentration of platinum has also been found in Greenland ice cores, dated to 12,890 BP with 5-year accuracy. This is interpreted as evidence against the Younger Dryas impact hypothesis by the study’s authors, but cited as evidence for the hypothesis by its proponents.[14][15]

Case Closed? Comet Crash Killed Ice Age Beasts
Spherules from archaeological sites in the study. The microscopic particles have marred surface patterns from being crystallized in a molten state and then rapidly cooled.
Credit: University of South Carolina

A space rock crashed into Earth about 12,900 years ago, wiping out some of North America's biggest beasts and ushering in a period of extreme cooling, researchers say, based on new evidence supporting this comet-crash scenario.

If such an impact took place, it did not leave behind any obvious clues like a crater. But microscopic melted rock formations called spherules and nano-size diamonds in ancient soil layers could be telltale signs of a big collision. The mix of particles could only have formed under extreme temperatures, created by a comet or asteroid impact.

Researchers first reported in 2007 that these particles were found at several archaeological sites in layers of sediment 12,900 years old. Now an independent study published in the Sept.17 issue of the Proceedings of the National Academy of Sciences (PNAS) says those findings hold up.

A team led by Malcolm LeCompte, of Elizabeth City State University in North Carolina, studied sediment samples from three sites in the Unites States: Blackwater Draw in New Mexico, Topper in South Carolina, and Paw Paw Cove in Maryland. The researchers said they found the same microscopic spherules in some of the same ancient layers as were found in the 2007 study.

A comet crash in the ice fields of eastern Canada could explain the region's die-off during the late Pleistocene epoch. While the cause of the catastrophic extinction event has been debated, researchers say it killed off three-fourths of North America's large ice-age animals, such as saber-toothed tigers and woolly mammoths, and the Clovis people, a Stone Age group that had only recently immigrated to the continent. [Album: 25 Amazing Ancient Beasts]

In the PNAS study, researchers tested levels of Clovis artifacts at Topper for the microscopic soil clues. The Clovis are known for their large, fluted spear points that they likely used to hunt large animals and which were first found near Clovis, N.M.

"If debris was raining down from the atmosphere, the artifacts should have acted as a shield preventing spherules from accumulating in the layer underneath," University of South Carolina archaeologist Albert Goodyear said in a statement. "It turns out it really worked! There were up to 30 times more spherules at and just above the Clovis surface than beneath the artifacts."

There is debate over whether a comet impact actually wiped out the Clovis, with a study detailed in 2010 in the journal Current Anthropology, suggesting the Clovis' nomadic lifestyle, and not a demise, could explain gaps in their occupation of sites.

An impact also would explain what set off the Younger Dryas period or "Big Freeze," a 1,300-year era of glacial conditions that has been well documented in ocean cores and ancient soil samples. A comet would have produced enormous fires that melted large chunks of the North American ice sheet, sending cold water into the world's oceans and disrupting the circulation of currents responsible for global heat transport, the researchers noted.

The wonder of our time isn’t how angry we are at politics and politicians; it’s how little we’ve done about it. - Fran Porretto
-http://bastionofliberty.blogspot.com/2016/10/a-wholly-rational-hatred.html

it is strange that this article doesn't mention the mountain of evidence uncovered since 2007 that the massive melting and resulting flood was caused by the impact of a comet or meteor into the glacial ice sheet covering north america then.

When they come up with evidence of a significant crater then I'll give the idea more credibility. To blow off the crater requirement by blithely saying of course the impact was on the ice sheet and therefore didn't leave a crater is to ignore that anything big enough to cause global (or just Northern Hemisphere) climate change would probably be big enough to punch through an ice sheet like it wasn't even there (especially at comet speeds). There is apparently evidence of impact craters on seafloors miles deep, but fans of the ice sheet impact theory would have us believe that an ice sheet is so much more massively solid than very deep liquid water that an impact wouldn't leave a crater trace behind.

For what it's worth, as far as I know the Younger Dryas is generally credited with killing off most (but probably not all) of the first humans in North America, leaving behind a more-or-less empty continent for the later wave of settlement via Siberia-Alaska.

Graham Hancock wrote an entire book on it.
Also look up Randall Carlson.

Yep and before that, there was Art Bell and Whitney Strieber - The BOOK (not the movie) The Coming Global Superstorm - which was the first time I saw information on this - Graham's book is later and better written on the details, but there was more public information out there by then.

expatriate Californian living in rural Ireland with husband, dogs, horses. garden and many, many cats

When they come up with evidence of a significant crater then I'll give the idea more credibility. To blow off the crater requirement by blithely saying of course the impact was on the ice sheet and therefore didn't leave a crater is to ignore that anything big enough to cause global (or just Northern Hemisphere) climate change would probably be big enough to punch through an ice sheet like it wasn't even there (especially at comet speeds). There is apparently evidence of impact craters on seafloors miles deep, but fans of the ice sheet impact theory would have us believe that an ice sheet is so much more massively solid than very deep liquid water that an impact wouldn't leave a crater trace behind.

For what it's worth, as far as I know the Younger Dryas is generally credited with killing off most (but probably not all) of the first humans in North America, leaving behind a more-or-less empty continent for the later wave of settlement via Siberia-Alaska.

so how big a crater do you think would still exist after a comet slams into a ice sheet 2+ miles thick at ~50,000 mph?

Nonetheless, the story is relevant because today, we’re watching another – or rather, a further – deglaciation, as humans cause a warming of the planet. There is also evidence that the Atlantic circulation is weakening again, although scientists certainly do not think a total shut-off is imminent, and are still debating the causes of what is being observed.

The validity of anything said from this point forward falls into question! YMMV

“Don’t pick a fight, but if you find yourself in one, I suggest you make damn sure you win.” - John Wayne

A continent size glacial lake poured instantly into the ocean. Causing global flooding. Instead of admitting this provides evidence of the Biblical flood they pretend that the much less yearly melt and refreeze cycle of floating ice is going to do the planet exact same thing.

Do they get more money if they find a stupid way to bring up global warming?

A continent size glacial lake poured instantly into the ocean. Causing global flooding. Instead of admitting this provides evidence of the Biblical flood they pretend that the much less yearly melt and refreeze cycle of floating ice is going to do the planet exact same thing.

Do they get more money if they find a stupid way to bring up global warming?

Biggest hole in their disaster prediction? We don't have any glacial lakes the size of Lake Agassiz. Don't see any forming, either.

Lake Agassiz was a really cool phenomenon. Being from Minnesota (the lake's southern edge), I've heard geological speculation about it, seen it's remnants/effects on our landscape all my life, including that we are still living with the weirdness of The Red River of the North (flowing north) and all of the kooky watershed issues in that region.

The geological research/new info is interesting and commendable, but mad speculation and predictions of (near) future disasters really are Art Bell/Whitley Strieber nonsense. A responsible journalist would have left off the second half of the headline.

The title Scientists may have solved.... Made me think of the modern often quoted lie "the science is settled" or what they say when they want you to agree with Al Gore.

It is not science when you manipulate data to match an agenda.

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Surely you're not saying we have the resources to save the poor from their lot. -JCSS
Friend, you cannot legislate the poor into freedom by legislating the wealthy out of freedom. And what one person receives without working for, another person must work for without receiving. The government can't give to anybody anything that the government does not first take from somebody.

The Earth warms and cools in cycles, sometimes dramatically. At the moment, we are entering a period of cooling. It could be quite disastrous, and no amount of SUV driving is going to turn that around.

Yup. Stopped reading the article, and moved on to the comments at that point. Once they start waving the man made global warming flag, it's difficult for me to take any of it seriously.

Sadly these days that is not a very good idea because I've noticed that nearly EVERY article having to do with anything involving the climate; especially anything suggesting that the world might be entering a low solar cycle/new solar minimum and/or impaired ocean oscillation with the potential to cool the climate in Europe and North American seems to be REQUIRED to come with these idiotic statements.

It is worse in the UK press than the US MSM, but it exists in both cases; your "give away" that it is an "add-on" probably put there by an editor is the absurd claim that somehow "global warming" will "prevent" the usual outcomes of climatic circumstances that can result in cooling climates, mini-ice ages or even full-on ice ages.

The "powers that be" (or whoever is pushing this idea) WANTS you to IGNORE any actual science that may be in the article, they know that most people will simply accept such statements at face value and the rest of us are likely to stop reading and reject any actual science in the article once we see such a statement in it.

In this case of this article, while there are a few other issues with it; it is mostly about some further evidence that the theory of a giant glacial lake melting at the start of the Younger Dryas caused masses of fresh water to enter the Oceans and moved the North Atlantic Oscillation South and created a "little Ice-Age" for about 1,000 years.

That idea is pretty much an accepted working theory (for now) to explain that event; the only debate is what caused the ice dam (or dams, there are discussions on if there was more than one event) to melt - was it just general warming that one day was enough to collapse the dam? Was it an asteroid strike or series of them (see Carolina Bays), could it have been one or more comets?

The only certain thing is that the world was warming, and de-icing and then suddenly for a thousand years (almost overnight) it got colder again but did not totally flip back into a full Ice Age.

That part is in the geological record, the how and why are a bit more open to question; the fact that things are slowing down now in the Atlantic is also a SCIENTIFIC FACT that can be measured.

Now what science doesn't know for certain is if the same climatic flip is likely to happen again and/or if it did would it be on a smaller scale like the 14th to 18th century "mini-Ice Ages" or might things reverse before things got to that tipping point?

What I really doubt that anyone knows (but nearly all these articles will say as if it is a fact) is that somehow by magic "man-made global warming" will prevent Northern Europe and parts of North America from cooling; no one knows that and again it seems to be a requirement to get this sort of article published in most main stream media to have to say it somewhere.

expatriate Californian living in rural Ireland with husband, dogs, horses. garden and many, many cats

so how big a crater do you think would still exist after a comet slams into a ice sheet 2+ miles thick at ~50,000 mph?

The general rule of thumb is that an impact crater on Earth is typically 20 times the size of the impactor. To cause long-term (more than 1,000 years, according to the OP) global climate change I would guess the impactor would have to be at least a mile wide and probably bigger than that. At some speed the difference between water, ice, and concrete becomes pretty much irrelevant to the thing falling. I have no idea what that speed might be, but I'd guess at something less than 1,000 mph. Comet speeds vary widely but call it 80,000 mph. At those speeds Earth's atmosphere also becomes pretty much irrelevant.

For what it's worth, the Chicxulub crater (the "dinosaur killer," six or more miles wide) extends "well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth" (https://en.wikipedia.org/wiki/Chicxulub_crater), with (I think) the initial impact melting much deeper than that. Which is why even a 2 mile thick ice sheet is highly unlikely to stop the impact cratering process. When it comes to comets it's less about the size and mass and more about the transfer of energy, and there's a lot of energy in anything travelling at comet speeds.

For what it's worth, the Chicxulub crater (the "dinosaur killer," six or more miles wide) extends "well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth" (https://en.wikipedia.org/wiki/Chicxulub_crater), with (I think) the initial impact melting much deeper than that. Which is why even a 2 mile thick ice sheet is highly unlikely to stop the impact cratering process. When it comes to comets it's less about the size and mass and more about the transfer of energy, and there's a lot of energy in anything travelling at comet speeds.

The dates don't match up or they're discussing two separate events which is highly unlikely. What's missing in this whole story is the smoking gun. The Carolina Bays where created by broken chunks of ice which melted afterward. I suppose we could test this by lofting an iceberg into space and seeing how much melts on the way back to earth. Reentry heat would be minimal since we're talking ballistic trajectory velocity not orbital velocity.

For what it's worth, the Chicxulub crater (the "dinosaur killer," six or more miles wide) extends "well into the continental crust of the region of about 10–30 km (6.2–18.6 mi) depth" (https://en.wikipedia.org/wiki/Chicxulub_crater), with (I think) the initial impact melting much deeper than that. Which is why even a 2 mile thick ice sheet is highly unlikely to stop the impact cratering process. When it comes to comets it's less about the size and mass and more about the transfer of energy, and there's a lot of energy in anything travelling at comet speeds.

it is hard to say exactly how big one comet or meteor might or might not have been to create the postulated effects (density, impact velocity, ice depth, etc), but if we posit a swarm, that problem goes away. just look back to comet shoemaker/levy breaking up before it slammed into saturn.

to me the sum of all the evidence is conclusive, whether it was one object or several.

it is hard to say exactly how big one comet or meteor might or might not have been to create the postulated effects (density, impact velocity, ice depth, etc), but if we posit a swarm, that problem goes away. just look back to comet shoemaker/levy breaking up before it slammed into saturn.

to me the sum of all the evidence is conclusive, whether it was one object or several.

I would think the overall energy released would be more-or-less the same whether it's a swarm or a single object. However, breaking an incoming space object into a swarm that peppers a much larger part of the globe/atmosphere might well cause more overall global damage than leaving it as a single object (which would "only" pound the snot out of the region it hits), particularly if it were a land strike rather than an ocean strike. As far as I know the general description of the comet strike in Lucifer's Hammer (mind you, it was only part of the comet at that) is still basically valid, with various details perhaps updated with more recent science, and especially since the Lucifer's Hammer impact was a swarm strike rather than a single impact.

By the way, the specific seafloor impact crater (still only a theory and not yet confirmed) I was thinking about when I referenced them in post #8 is Burckle Crater (https://en.wikipedia.org/wiki/Burckle_Crater). The incoming object (possibly a comet) was perhaps a mile wide (if you take the theorized 18 mile wide seafloor crater and divide it by 20 to get the rule-of-thumb ratio, although I don't know if that's still valid when you're talking about deep seafloor cratering) and is in about 12,500 feet of water. Maybe people are thinking they can scale up their personal experience of throwing a chunk of ice at a frozen pond in order to accept the idea that a comet hitting an ice sheet would leave no lasting trace behind, but that's simply not the case when you get to miles-wide objects traveling at asteroid or comet speeds.

A continent size glacial lake poured instantly into the ocean. Causing global flooding. Instead of admitting this provides evidence of the Biblical flood they pretend that the much less yearly melt and refreeze cycle of floating ice is going to do the planet exact same thing.

Do they get more money if they find a stupid way to bring up global warming?

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